Cold water dispersible starch sizes and process of making them



Patented Feb. 16, 1954 com WATER nIshERsIB STARGH s zing 41m rgocEss OFMAKING THEM ha ph W. K rr Ri er and Walter J. E t e s, ak 12th, i lsshhrs #9 604 fimi eh efini iq hpany, N ark, N @9513? ration of NewJersey No Dravyjgg,

Arnh Au ust 3% 525 14 Giaixns.

This mwhtiqn relates t9 h nrsducti h 9i modified sta ch produc s, and mmpart sulai'ly cold water dispersible starch products,

An .Qbject of this. i v htioh h; evi-de a Praccss to; the p odhhti h ata .d y starch P194119; which is rap dly disps siblc h d'hish ys ihb ccold wat s: and the hrhhh thhrshf, A ihrths Qba'ect is thc phoclhctioh,f shgh protl sts Wit. high rate of solution in cold water. Still afur-,- thsr chi-est th pr dhht hh 9.1 such prh h especially adapted .forlahhdh llflthfi; Qbisct s th pm t oh su h rodu ts whi h, Whfin h hplq cdsi ng e eralt ohs, exhibit acccptablc stihchihs .aluh; uni ormit coaths, relht h a dam i chi at r sh t ting on a fabric when the latter issized, dr ed, and spiiihh hd waist and h s abil ty o create a shicothflexible Wheh ,ia ris s zed thc sw th is xo hd- Varicus methods have hcn .smplpy d the ast in. hfiorts to pbtaih sa isiac yry sold W 1 i?! diser ibic cold hts s luble stanch produc s Q cmsthsld n olves pas n hqistStarch hltcrtcak betw en iga d ail and grindin the dried, hgel t hizcdmduht o p w er However, this material disperses in 919 Whth 9h withgreat dimculty, and exact; with nmhhscd stirrin on M 1;! about ,5 to 1.0per ent 9f the teriai actu l1-1i91- M911? ,hhhchtl has been partia l hydconverted starch gelati ed and dried b pass.-

.an aqu us s u ry .hsween hsatsdmllsfli pmduct also disnersa h d water.ohiy with grea difiiculty and less than v2 ,psrcshth 12h? material t shually dissolves.

Still inane m smly thsxe has hash btai ed .a sta ch sui ble ta use alaundr size wh ph disperses rapidly in cold water and rapidly gissolvesthere n 9 the exte t of alight lnenes t, This is accomn shcd .b-y h dhlxzihg th starch t a :QW viscos ty le el tbfy means .of an hnzymetreatmem, hollowed by hoh l ly rgs h tini ins and d yi g th pp eredstarch heated rolls. Such process is the subject of a copending patentapplication, U. S. Serial No. V

28;.416, filed May 21, 194% Patcnt .NQ- 3 509,3 Thism odhet, h w ver, athnh h a stash .imprpvh- .mentpver pissvious pnddzucts, i ilsewisehot hmpleteiy SatiSfaCJJQ Y,JDtLfiIIWQhQS if .it s icsz c r rtsd suhicient yts obta n ra ti ally ihsfiahiahhous his ct hi ity and high so ubilitx.it s bits a tendency toward water's pott ng whhhiab iqs an? sized withit, when drie and spirihkla w th water. wh n cqh ented :to ,a spmewhat 1.5. 33 dcgrcc. water spmtihg 99$ hvidchlz y; th

ad wi h h d a thi a sh m Wheat. etc" 9? h urc i h df. t ey in Likcwiscis; e he s reasimh d u Wm: hhiqrits i the r f rred di n hh eh ihhushther qis ea i re g m h m pioyed, such as per com-pounds, and esgeciaiigsoluble peroxides, particularly sodium, calcium and hydrogen peroxides;persulfates, perborates, chromates, and dichromates, usually employed inth form of their sodium salts; nitrogen'idi: oxide; a W6 1} as sodiump-toiuenesu'lfoneoh iops am de "s d under the h derk h F amine-T; etc.In addition to the economic advantage, sodium; 'hypoehior'ite offers theadded advantage that colorless products may he tamed 91? d ly.

Flt i 961. 3. 1 h m d? wh iht dhh l i Ill? PIPdP i Q s h yl 1, 95:hyshoxyl sr hps in th sawh gh-hs suhohsssmeh y t e q h e wh m e hm t do eve be w t a t whieh t s i h calsdm a tbs st t h 1M9 9 me ech h weightbphi s hqhura the laws; 1 th? or 1 .9 valu I s P1195 9 h s h may th cenhisht ylie hwsd hy ris qsity ,Ii 199 iehhd tha a isiahsah 9; 1.? ih qhto paste viscosities wi n 11 M. J, ,Y' LUI'; vnml 4 pier .lhph

5,25 straw 9 12. 9 Wat l a is t9 madhsts uhighhe 99am? -hr9pc .h ,to ldwat r d spcrsihls stench prohuht- .iz hch shimsaxihs 91B Tnrst h P139"cedure, the preferred oxidation rang sta ch h;3.89.; 1. f Wate Forreasons of conveniencg inti ra t 3 h equipment is generally readilyavailable in starch milling or processing plants, the starch ispreferably treated with the oxidant in the granule stage as an aqueoussuspension at temperatures below the gelatinization point of the starch.This method also possesses the added advantage that the oxidized starchmay be readily purified from undesirable by-products which impair itscolloidal properties by the simple expedient of filtration and washingwith water. Oxidation in the granule stage offers a further advantage inthat the oxidized starch may be readily dehydrated by conventionalstarch drying equipment, thereby permitting storage or transport to adistant location for subsequent stages of the process, if it should bedesirable that the process be discontinuous. However, if desired, theoxidation may be performed on gelatinized starch, particularly incertain instances where by-products offer no problem, such as oxidationwith hydrogen peroxide.

At some stage in the procedure the starch must be substantiallycompletely dispersed and gelatinized. By complete gelatinization anddispersion, we means gelatinization accompanied by mechanical disruptionof each starch granule so as to obtain a dispersion of substantially allof the starch molecules. The particular stage of the process, i. e.before, during, or after, oxidation at .which this takes place is mostcritical. However, the starch should be as completely dispersedaspossible when subjected to dehydration for production of the finalproduct.

The means by which the substantially complete dispersion andgelatinization is accomplished are not critical. One satisfactory modeis by the use of higher temperatures and application of shearingstresses to the swollen starch granules, such as are obtained, forexample, in

homogenizing equipment. The preferred equipment for use in the presentprocess is a Votator, operated at temperatures in the region of about 90to 95 C.

The Votator device of such design that it provides a high ratio ofsurface to volume, coupled with intense mixing or agitation, wherebyviscous or paste type material may be quickly heated. Basically, theVotator consists of a jacketed heat transfer tube-in which is provided amechanically driven rotator of such dimension as to leave a relativelynarrow annular space between the inside of the .tube and the exterior ofthe rotator. The rotator :is provided with a plurality of scraper bladesand is adapted to be revolved at several hundred R. P. M. The heatingmedium is ;the jacket on -.the passage of the starch paste though thean- ,nular space therewithin. Only a small amount of ,the starch pasteis .time, and because passed through the heating tube countercurrent toin the Votator at any given of the high heat transfer surface coupledwith the agitation and scraping effectsprovided by the scraping blades,the starch paste is brought up to the desired temperature in arelatively 'short period.

, A number of United States patents have been issued which are directedto the Votator and various methods of using the same. Reference ,is madeto United States Reissue Patent No. 22,519, reissued July 18, 1944, fora more detailed description of the construction and operation of -;theVotator.

The Votator, as used in our process, may

be supplied with either water or steam as the heat transfer medium.

is functionally a heat exchange The use of the Votator enablescontinuous operation of the present process and the use of relativelyconcentrated starch liquor, thus increasing the output possible for agiven volume capacity and minimizing the amount of water which must beevaporated during the dehydration step.

Although the Votator is particularly adapted for procuring the completegelatinization required in this process, any other equipment orprocedure which accomplishes complete dispersal of the starch substancemay be employed in the gelatinization step. For example, a heatedmixture of the starch and water may be pumped under pressure through thefeed orifice of the spray drier.

When the gelatinization has been completed, the starch sol should beheld under conditions optimal for maintaining the dispersed phase and.least conductive to reassociation of the molecules until the starch isdehydrated. Higher temperatures and agitation are helpful in maintainingcomplete dispersion.

The starch sol is finally dehydrated. Ourpreferred equipment for thedehydrating procedure is a set of heated double rolls, although otherforms of dehydrating equipment suitable for drying starch pastes, suchas spray driers, may also be used.

It has been found that the mechanics of the dehydration process and thetendency to form a uniform and more readily redispersible product arematerially benefited by incorporating from about 3 to about '7 percentboric acid into the starch sol being fed to the dehydrating equipment.

It has been further found that the starch may be very nearly completelygelatinized almost simultaneously with the dehydration by feeding aslurry of the starch to heated rollers, providing the starch has beenoxidized to the upper limits indicated above, i. e. the paste viscosityof the starch by Scott test is of the order of about to seconds per 100ml. for 100 grams of starch in 280 ml. of water. However, even at thislevel I there is some sacrifice in stiffening power of the cosity byScott test prepared starch and more tendency for the size to water-spot.Therefore, particularly at lower levels of oxidation, it is preferablefor best results that the starch be gelatinized in a separate operation,as described above.

For maximum rate of redispersion, it is necessary to grind the driedproduct to a powder, unless it leaves the dehydrating apparatus in apulverulent form, as for example, in spray drying. The preferredparticle size is such that the powder will pass mesh sizes between 30and 120 mesh.

The examples set forth below, which are intended as typical andinformative only and not in a limiting sense, will further illustrateour invention. Tests used in characterizing the products obtained willbe described hereinafter.

EXAlVIPLE 1 Corn starch was suspended in water at a densitycorresponding to 20 B. and treated at 25C. by stirring with a solutionof sodium'hypochlorite which contained, based on weight of starch, 6percent available chlorine and 1.5 percent free alkali. Afterapproximately 15 hours, a sample of the starch after washing showed apaste visof 50 seconds per m1. using 100 grams of starch in 280 ml. ofwater.' 'The starch was then filtered andwashed'w'ith w'at'er until itwas substantially free of chlorides and approximately neutral inreaction.

The starch was then suspended in fresh water to make a slurry atapproximately 20 B. and percent boric acid was added, based on starch.This slurry was fed to rolls heated by steam at 90 p. s. i. on which thestarch was gelatinized and dried. The resulting flake was ground to passa 35 mesh copper sieve, and fines passing a 120 mesh sieve wererejected.

Dispersibility rating of this product in water at 25 0. was seconds.Approximately 9-? percent of the starch product dissolved. When fabricwas immersed in the size, wrung and ironed, stiffening value, asdetermined by Flexometer readings, was 97 ercent of that imparted by a 4percent cooked paste of a conventional laundry starch (Linit brandlaundry starch). Fabrics sized with the roll-dried product showed lessmasking, a more flexible and more natural feel and appearance then whensized with the cooked, conventional starch. Evenness of applied size, asevidenced by freedom from streak marks on dark goods, was substantiallythe same in both instances.

When the sized goods were sprinkled with water and dried, rating forwater spotting imparted by theroll-dried product was 3 and for theconventional laundry starch l.

EXAMPLE 2 Example 1 was repeated except that 3 percent boric acid wasadded to the starch fed to the rolls. Results obtained were similar tothose 0btainedin Example 1, except that the dispersibility rating of theproduct of Example 2 was seconds.

EXAMPLE 5 A blend of 60 parts by weight of wheat. starch and parts byweight, of cornv starch was, oxidized, as in Example 1, except thatapproximately 6 percent available chlorine was used. The paste viscosityof the starch after oxidation 'Was by Scott test seconds per 100 ml.using 100 grams of starch in 280, ml. of water. Dispersibility rating.of the final product was 15 seconds and the water spot rating was 3.

EXAMPLE 6 Example 1 was repeated with the exception that in theoxidizing step only approximately 4 percent available chlorine was usedand the paste viscosity of the starch fiber oxidation was by Scott test90 seconds per 100 ml. using I00 grams of starch in 280 ml. of water.

'Dispersibility rating of this product in cold water was. only fair, ie.about 80 seconds, althrough substantially all of the starch eventuallydissolved. The water spot rating was nowonly 2.

Example 1. was. repeat d except that in. the oxidation step only 2percent available chlorine was added and, the starch had a paste,viscosity by Scott test of 125 seconds per 100 ml. using 100 grams ofstarch in 280. ml. of water.

Dispersibility rating of this. product in cold water was poor, i. e.,3.00 seconds,- and the product generally unacceptable.

Corn starch was: oxidized as. in Example .1. After the starch was washedit was suspended in fresh water at. a concentration of approximate,- ly35 percent, 5 percent boric acid was. added. based on starch, and the.liquors were passed continuously through a. Votator heated with steam sothat the starch was heated to approximately C. Thereafter the.completely gelatinized paste was fed continuously through a pipe, main.-tained atv 90-95 (3., directly to the valley between two rolls. heatedwith steam at. 65 p. s. i. On these the starch sol was dehydrated to aflake. The flake was ground to pass a 35 mesh wire screen and finespassing a 120 mesh screen were rejected.

Again a roduct was. obtained which has properties similar to those ofthe product of Example 1, including a water spot rating of 3.

EXAMPLE 9 7. body, the fabrics had a softer and more flexible feel anda. more natural appearance. Water spot rating was 2.

EXAMPLE 10 Corn starch was treated, as in Example 8, except thatoxidation was so limited (by the amount of oxidant) that the oxidized.starch had a paste viscosity of 53 seconds per m1. using 40 grams ofstarch. per 280 ml. or 35 seconds per 100 ml. using 28.35 grams. ofstarch.

This product had a dispersibility rating in cold water of 10 seconds,and approximately 92 percent dissolved. Fabrics sized with thispreparation had very much more body than when sized with a freshlycooked conventional laundry starch at equal weight concentration and amore smooth, flexible and brilliant appearance. Moreover, the water spotrating of this starch. was 0.

Comparing the results of Examples 1, 6 and 7 with the results ofExamples 9 and 10, it. is apparent that in order to make an acceptablecold water dispersible textile size by roll drying a slurry of oxidizedstarch, the starch should be oxidized at least to the viscosity levelindicated in Example 6; if lesser degrees of oxidation are employed,such as used in Example 9, an acceptacle product may be made ifgelatinization is per-v formed in a separate operation. as by use of a.Votator."

Analytical methods employed in testing the product produced according tothis invention are as follows:

Cold water dispersibility measurements are made as follows:

A specially constructed funnel, either of glass or metal, capable ofholding 500 ml. of aqueous liquid and to which is attached a screen 1.75sq. cm. in area and having '70 meshes to the inch is required in thisdetermination.

Twenty grams of the starch to be tested are weighed on a torsion balanceand added to 400 ml. of water at a temperature of 77 F. (25 C.) in aliter beaker. 'The dispersion is agitated with a four fingerbreaker-type agitator revolving at 280 R. P. M. The starch product isdispersed for exactly 45 seconds.

At the end of the time interval, the dispersion is rapidly transferredto the funnel described, which is supported over a 500 ml. graduate. Thetime required for a given volume of dispersion to pass through thefunnel is considered the dispersibility rating. The less time requiredto collect a definite volume of filtrate the better is the rating of theproduct.

By this procedure ratings are as follows:

Excellent=l second or less for 400 ml. Good=l5-60 seconds for 400 ml.Fair=60120 seconds for 400 ml. Poor=More than 120 seconds for 400 ml.

Cold water solubility determinations are made as follows:

Weigh accurately a 2 gram sample of the starch to be tested and transferit carefully to a dry 200 ml. centrifuge bottle. Add exactly 99 3,

ml. of distilled water and shake vigorously as soon as the water comesinto contact with the starch. Stopper the bottle and shake mechanicallyfor minutes. Centrifuge the bottle containing the sample for 15 minutesat approximately 2000 R. P. M. Pipet accurately a ml. aliquot of thesupernatant solution into a dry, tared nickel or silica dish. Evaporatethe sample to dryness on a steam bath or in an air oven at 100 C.Complete drying by placing the sample in a vacuum oven at 105 C. for 4hours. Remove sample from oven, cool in desiccator and weigh.

Calculation:

Flexometer sizing value determinations are made as follows:

Materials and equipment (1) Schiefer Flexorneter and accessories 1 (2)Electric mangle (3) Mechanical wringer (4) Storage space at constanttemperature and humidity (5) Loosely woven cotton fabric such as muslin,longcloth or cambric (approximately 0.010 inch thick and of a threadcount of approximately /50) (6) Pabst Ex-Size for desizing the material(7) Reference Standard (Commercial laundry starch prepared in crystalform by drying GO-fluidity, acid-modified corn starch) Preparation ofmaterial.-Desize the material by soaking overnight in a solutioncontaining 10 ml. of Pabst Ex-Size" per liter of solution.

The Flexometer, an Instrument for Evaluating the Flexural Properties ofCloth and Similar Materials, by H. F. Schiefer, ResearchPaper No. 555,Bureau of Standards Journal of Research, vol. 10, pages 647-57 (1933).

Wash the desized material through 2 sets of soapsuds and rinse withwater 5 times, using distilled water for the last rinse. If the desiredsample is dry, immerse in distilled water and put through the wringerjust before sizing. The cloth should be torn into test strips 36 incheslong and 6 inches wide before sizing.

Preparation of sizing solutions: Reference standard.Weigh 20 grams ofreference standard starch into a 1 liter beaker and add 450 ml. ofdistilled water. Stir the mixture until the starch is suspended andplace the suspension over a Bunsen or Fischer burner. Stir continuallyuntil the starch is gelatinized and bring the solution to a boil. Boilfor 4 minutes. Cool the solution to room temperature (TO-78 F.) andadjust the net weight to 500 grams. Stir the solution and cover untilready to use.

Cold water dispersible, cold water soluble starch sample.-Weigh 20 gramsof the starch to be tested into a 1 liter beaker. Add 480 ml. ofdistilled water at room temperature (70-78" F.) and stir vigorously asthe water comes in contact with the starch. Mix 3 minutes with amechanical stirrer (propeller type) and inspect the solution forundissolved particles. If necessary, mix until no undissolved lumpsremain. Cover the solution until ready for use.

Sizing the fabrics.-The cotton fabrics (6" x 36") which have beenpreviously dipped in distilled water are put through the wringer. If notused immediately, they are kept in a covered beaker. Immerse the testsamples in the starch solution and stir for 1 minute. Allow the sampleto remain in the starch solution for 2 additional minutes. Adjust thepressure on the rolls of the wringer and do not change this pressuresetting while running a series of samples. Wipe the wringer rolls with adesized towel wrung from distilled water after each starched sample iswrung through. Now put the sample through the wringer and place in acovered beaker until ready for ironing.

Heat the electric mangle until the temperature reaches 450 F. Put adesized cloth over the mangle roll and leave in position. Now iron thesample until it is dry; 2 or 3 revolutions are usual-,- ly sufiicient.Each sample must be ironed on a freshly desized cover over the mangleroll. The ironed samples are then conditioned at least 12 hours in theconstant temperature room (73 F. and 50 percent relative humidity).

The sample is then cut into strips 2 inches by 6 inches, which aretested with a Flexometer.

Measurement and calculations.--A test strip is placed on the mountingblock and clamped in position. The mounting clamps are then afiixed withCanada balsam. The specimen is removed from the block and the excessmaterial is out 01f, leaving the sample 2 inches by 4 inches. Sixteensuch specimens are prepared from each sample. The specimens are mountedon the Flexometer and the spring deflection is determined as outlinedbelow. The average result obtained on 8 such pairs of samples is thespring deflectionfor the sample. v

After the samples are mounted on the Flexom eter, the movable plate isrotated to lower scale reading of 10. The upper scale reading is noteddry substance basis and recorded. The upper scale reading minus thelower scale reading is the instrument blank. Now the movable plate isrotated to lower scale reading of 72 over a period of 10 seconds. Themov able plate is held at this reading until 30 seconds have elapsed andthen the upper scale reading is noted and recorded, while, the lowerscale is held at a reading of 72. The difference between the upper scalereading and the 72 minus the instrument blank is called the springdeflection at a folding angle of 3 degrees. The deflections forreference standard starch and cold water dispersible, cold water solublestarch are then compared and the stiifness of cold water dispersible,cold water soluble starch is expressed in terms of the referencestandard.

Percent stillness (Relative to ref erence standard) Cold waterdispersible, cold water soluble starch spring defi ection X 100Reference standard spring deflection Sample Calculation Cold WaterDispersible, Cold Water Soluble Starch Reference Standard Lower ScaleUpper Scale 1 Lower ScaleUpper Scale Reference standard springdefiection=l2.0 Cold water dispersible, cold water soluble starch springdefiection=13.2 Percent stiffness (Relative 132x to referencestandard)=" goods which have been sized with various starches atapproximately 5 percent concentration and ironed, by placing 5 drops ofwater in one spot on the surface of the fabric and noting the intensityof the ring mark which develops on evaporation of the spot of water. Onan arbitrary scale, native corn starch has a rating of zero,conventional laundry starches (such as Linit brand laundry starch) arating of one and cold water dispersible laundry starches of the priorart (such as produced according to copending application U. S. SerialNo. 28,416, filed May 21, 1948, Patent No. 2,609,326) a rating of 3 to4.

We claim:

1. Process for the production of a cold water dispersible, cold watersoluble textile size comprising treating starch with an oxidizing agent,substantially completely gelatinizing and molecularly dispersing thestarch, and hydrating the starch paste; said dehydration beingaccomplished in the presence of from about 3 to about 7 per cent ofboric acid, based on the weight of the starch, said boric acid beingadded to the starch after oxidation but prior to dehydration; thetreatment with said oxidizing agent being carried on until a sampleexhibits a paste viscosity by Scott test within the range of about 125seconds per 100 ml. using 100 grams of starch in 280 ml. of water toabout 35 seconds per 100 ml. using 28.35 grams of starch in 280 m1. ofwater.

2. Process for the production of a cold water dispersible, cold watersoluble textile size, comprising treatin an aqueous slurry of starchwith an oxidizing agent at a temperature below the gelatinization pointuntil a sample of said starch exhibits a paste viscosity by Scott testwithin the range of about 125 seconds per 100 ml. using 100 grams ofstarch in 280 ml. of water to about 35 seconds per 100 ml. usin 28.35grams of starch in 280 ml. of water, filtering and washing the oxidizedstarch and adding thereto boric acid and then passing the starch overheated rolls to gelatinize and dehydrate the same; the amount of boricacid being about 3 per cent to about 7 per cent, based on the weight ofthe starch.

3. Process according to claim 2 wherein said oxidizing agent is sodiumhypochlorite and said starch is corn starch.

4. Process according to claim 1, wherein said oxidizing agent is sodiumhypochlorite.

5. Process according to claim 1, wherein said oxidizing agent is asoluble salt of a per compound.

6. Process according to claim 5, wherein said per compound is a solubleperoxide.

7. Process according to claim 1, wherein said oxidizing agent isnitrogen dioxide.

8. Process according to claim 1, wherein said oxidizing agent is sodiump-toluensulfonechloramide.

9. Process according to claim 1, wherein said dehydration is carried outby spray drying.

10. Process according to claim 1, wherein said starch is corn starch.

11. Process according to claim 1, wherein said starch is wheat starch.

12. Process according to claim 1, wherein said starch is grain sorghumstarch.

13. Cold water dispersible, cold water soluble starch, producedaccording to the process of claim 1.

14. Cold water dispersible, cold water soluble starch produced bytreating starch with an oxidizing agent until a sample exhibits a pasteviscosity by Scott test within the range of about 45 seconds per 100 ml.using 100 grams of starch in 280 ml. of water to about 35 seconds per100 ml. using 28.35 grams of starch in 230 ml. of water, substantiallycompletely gelatinizing and molecularly dispersing the starch, anddehydrating the starch paste in the presence of from about 3 to about 7percent of boric acid, based on the weight of the starch said boric acidbeing added to the starch after oxidation but prior to dehydration, andbeing dispersed in cold water within at least about seconds and having awater spot rating not exceeding about 3.

RALPH W. KERR. WALTER J. KATZBECK.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,020,655 Perkins Mar. 19, 1912 2,424,050 Pecker et al. July15, 1947 2,541,773 Lokema et al. Feb. 13, 1951 2,559,043 Nestor July 3,1951 FOREIGN PATENTS Number Country Date 179,765 Great Britain May 18,1922 188,992 Great Britain Nov. 23, 1922 412,377 France July 11, 1910

14. COLD WATER DISPERSIBLE, COLD WATER SOLUBLE STARCH PRODUCED BYTREATING STARCH WITH AN OXIDIZING AGENT UNTIL A SAMPLE EXHIBITS A PASTEVISCOSITY BY SCOTT TEST WITHIN THE RANGE OF ABOUT 45 SECOND PER 100ML.USING 100 GRAMS OF STARCH IN 280 ML. OF WATER TO ABOUT 35 SECONDS PER100 ML. USING 28.35 GRAMS OF STARCH IN 280 ML. OF WATER, SUBSTANTIALLYCOMPLETELY GELATINIZING AND MOLECULARLY DISPERSING THE STARCH, ANDDEHYDRATING THE STARCH PASTE IN THE PRESENCE OF FROM ABOUT 3 TO ABOUT 7PERCENT OF BORIC ACID, BASED ON THE WEIGHT OF THE STARCH SAID BORICACID, BEING ADDED TO THE STARCH AFTER OXIDATION BUT PRIOR TODEHYDRATION, AND BEING DISPERSED IN COLD WATER WITHIN AT LEAST ABOUT 80SECONDS AND HAVING A WATER SPOT RATING NOT EXCEEDING ABOUT 3.